(1) Field of the Invention
The present invention relates to a displacement sensor which detects displacement such as the rotation of an internal-combustion engine.
(2) Description of the Related Art
Several kinds of sensors have been proposed in the prior art, such as an electro-magnetic pickup construction having an pickup coil, a magnetic resistance element construction, a Hall element construction, as shown in Japanese Examined Patent Publication (Kokoku) No. 58-42412, or a photo-interrupter construction, and so on, as displacement sensors, particularly rotation sensors for detecting rotation.
In the prior art sensors having an electromagnetic pickup construction, a problem arises wherein the output voltage changes in accordance with the rotation speed, the construction is complicated, and the cost is high because of the necessity of winding the pickup coil.
In the prior art sensors having a magnetic resistance element, Hall element, or photo-interrupter construction, a problem arises in that it is necessary to provide a drive power source.